Use non-symmetric example.

[HansOlsson]

Closes #2749

[HansOlsson]

I don't think that making the matrix square would give much, but it would be simple - just iterate over n and m instead of n.
Note that the original example actually lacked an ending semi-colon.

[perost]

There's a syntax error on the first line still, ] instead of }.

[HansOlsson]

There's a syntax error on the first line still, ] instead of }.

I think I committed and pushed that now, but it doesn't show up on github yet.